Experimental study on the deflagration and flame‐development characteristics of hydrogen‐blended natural gas flames under various initial conditions

Hydrogen‐blended natural gas (HBNG) is an effective transitional solution for large‐scale hydrogen energy transportation, whose safety requires quantitative assessment from a practical perspective. This study constructed a 60 L cylindrical deflagration experimental setup, conducting deflagration tests on 30% HBNG at an equivalence ratio of 1 under initial pressures of 1, 1.2, 1.5, and 2 atm, with a control test of 80% HBNG at 1 atm. High‐speed schlieren imaging and dynamic pressure monitoring were adopted to reveal how different conditions affect the HBNG deflagration characteristics. Results show that raising the initial pressure from 1 to 2 atm increased the maximum deflagration overpressure from 0.947 to 2.091 MPa and the maximum pressure rise rate from 5.66 to 17.7 MPa/s, along with faster flame propagation. Initial pressure has a more significant effect on HBNG maximum explosion pressure, while hydrogen blending ratio has a more pronounced impact on flame development. The peak pressure of 30% HBNG at 2 atm is 44.2% higher than that of 80% HBNG at 1 atm, with a 90.32% longer time to reach peak pressure. These findings provide critical data for pressure specifications in the safety design of transportation pipelines and differential risk assessment for hydrogen‐blending scenarios.